Desulfator Noise

Dear Home Power, I am going to build the lead-acid batterydesulfator as shown in HP77. I also have been looking at the two desulfators advertised in HP I have two technical questions.

Will the pulse affect my digital cell phone, and if so, can it be shielded? We are about nine miles off the grid and it is our only means of communication. We have it tied into our 12 V battery.

Second, the TtW! article indicated that the Solar Boost MPPT charge controller works on the maximum output voltage of the panels, which in my case can reach almost 19 V open circuit. The desulfator article indicated a maximum voltage of 16. I don't know what the maximum connected voltage might be, but it might exceed 16 V if it can freewheel. Will Greenslate, Mosier, Oregon

Hi Will. You will not notice noise from the desulfator in your cell phone because the power level of the pulse is very low and the battery acts as a filter. We have run two different brands of electronic desulfators here for years and have noticed no RFI on our cell phone, radiotelephones, HF ham radios, and 2 meter ham radios.

The open circuit voltage of the PV array will not be a factor because the voltage of anything connected to the batteries is battery voltage, not PV open circuit voltage. Under normal charging, your batteries will probably not get above 15 VDC. But during equalization, your batteries could be significantly higher; 16.5 VDC would not be unusual. Simply add a forward biased silicon diode to the positive input lead of the desulfator. This will drop the incoming voltage by 0.75 VDC. Richard Perez

The Right Voltage

After reading Home Power for a few years off the newsstand, we finally purchased a subscription and love your magazine.

We've been off the grid for almost a year now and have a few questions regarding our solar-electric setup. First, it's tiny—three 60 watt Kyocera panels, a Solar Boost 50, and six Exide GC4A batteries. We're learning that November is extremely overcast here in northeastern Vermont and we get very little charging capacity. The only system monitor we have is battery voltage. My first question is what is true battery voltage? Last night when I shut off the inverter, the batteries measured 11.8

volts. This morning, after sitting idle all night, the were at 12.0. Which is correct? When I turned on the system last night, the batteries were at 12.2, but they were down to 12.0 within 30 minutes, and 11.8 after three hours when I shut everything off.

My second question is about alternative charging. The batteries are just inside the back door. Could we drive the car up next to the door and run jumper cables in to the batteries? We would have the charge controller disconnected during charging. We have no backup generator.

And finally, we recently replaced our Trace C30A+ charge controller with the Solar Boost 50. Is this unit too big for our existing system? We plan to add a few more panels and possibly an Air 403 wind generator next year.

Hello Dan. Battery voltage is not an accurate indicator of battery state of charge. You need a battery ampere-hour meter such as the Tri-Metric or E-Meter. Battery voltage fluctuates with current transfer. When the battery is being discharged, the voltage goes down— the heaver the discharge, the lower the voltage. When the battery is being charged, the voltage goes up—the heavier the charge, the more the voltage rises.

It is possible to hook up your car to the battery and recharge it. But this is terribly inefficient—you'd be running a 100+ hp engine for a load that is really less than 5 hp. Also, unless you bypass or adjust it, the car's voltage regulator will keep the battery from being charged very much, since it is normally set to keep your starting battery at about 13 volts. In the download section of our Web site, there is an article on how to build a DC generator using a lawn mower engine. It's cheap, efficient, and very effective.

The Solar Boost is a great regulator. Having a regulator that is oversized is an excellent idea. It allows you to expand the system without replacing the regulator. Richard Perez

Need A Diversion, & Controller Set Points

Dear Richard and the crew, If the following topic has arisen in the past in Home Power, we missed it, so we hope that we are not going over old ground.

We are trying to figure out how charge controllers and diversion load controllers interact. We have a Trace PC-500 power centre, with a 60 amp PWM charge controller onboard, handling our 1,350 watts of PV power. A 1,500 watt Bergey wind turbine is also hooked up to the battery bank through the PC-500, but the turbine has its own charge controller. So both charge controllers are sensing the same battery bank.

Our challenge comes when we try to incorporate a diversion load controller to pick up any excess power and dump it into our 115 gallon domestic hot water tank. The two charge controllers work on battery voltage and taper off their input depending upon that reading. So how do we incorporate a diversion load controller that also only operates when a battery voltage reading above a set level is detected? It would seem that the charge controllers never permit the battery to rise above a set voltage (except when equalizing)—that's their job. So how does a diversion load controller get a piece of the action?!? We are beginning to wonder whether it is an either/or situation; charge controller or diversion load controller, but not both. Can you shed any expert light on this for us, please?

Second question; I recently purchased a TC60 charge controller to act as a diversion load controller. The main charge controller is located in a PC500 power centre. The whole system is still being set up and tweaked. The batteries are HUP Solar-1s, 1,900 AH, configured for 24 VDC. Manufacturer's voltage settings for these batteries are: Bulk = 29.6 V; Float = 27.0 V; Equalise = 30-31 V.

My query is whether these latter settings are satisfactory to permit a smooth diversion of incoming power from the batteries to the water heating element dump loads when the batteries are fully charged. Or do the TC60 voltage settings need to be further apart from those of the main charge controller and, if so, in what direction?

As you can tell, my knowledge of things electrical is pretty basic (read "Nil"!), so any help or advice you can provide will be mucho appreciated! George & Lynn Mycroft • [email protected]

Hello George and Lynn. The answer to the first question is really very simple. Set both of the existing charge controllers up by 0.1 VDC, then set the new diversion controller 0.1 VDC lower than the other two controllers. This way the diversion regulator will operate first. If the hot water heater is fully heated, then either of the two other controls will operate.

Those controller set points sound just fine to me for a room temperature battery. The only question I have is: How long does the battery remain in bulk charge mode before reverting to float mode? I'd recommend at least five hours. Richard Perez

Desulfators & Equalization

Thank you for your recent advice on checking my batteries. I charged them and checked specific gravity, and found the bad ones. My battery bank has never been better (still have eight good ones)!

Additionally, I installed a desulfator. My question is, do I still need to equalize them? If I do, how high should the equalizing voltage be, and for how long? The batteries are Interstate Workaholics (around 200 AH @ 6 V), about 5 to 7 years old. Roy D Surovec, Edwards AFB, California • [email protected]

Hello Roy. The desulfator will work many wonders, but eliminating the need for equalizing charges is not one of them. You still need to run periodic equalizing charges. An equalizing charge is a controlled overcharge of an already fully recharged battery. Raise all voltage limits on controls, and overcharge the battery, at no faster than the C/20 rate, for five to seven hours. Voltage may get as high as 16.5 VDC (especially if the battery is cold).

Perform the equalizing charge every three to four months, or every five to seven deep cycles, whichever comes first. Have plenty of distilled water on hand. Equalizing charges will use up lots of water, and since the electrolyte is doing the rolling boil, this is the absolute best time to water the cells. Richard Perez

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.